Superior Parts SP 502976U Aftermarket Piston Driver for Paslode / Duo-Fast DF225C Coil Siding Nailer - US S7 Material. This is a generic replacement driver with o-ring for the Paslode DF225C Coil Siding Nailer. This comes with a patent pending locking mechanism which will not allow the driver to unscrew from the piston. Aluminum is crimped into the unilok grooves of the shaft to prevent unscrewing. Guaranteed never to unscrew.